Method for flashlamp stabilization



Jim 5, 1970 'c. D. BEINTEMA ET AL 3,488,547

METHOD FOR FLASHLAMP STABILIZATTON Filed Dec. 15, 1966 A va/701:.

United States Patent flice 3,488,547 Patented Jan. 6, 1970 3 488,547 METHOD FOR FLASHLAMP STABILIZATION Chester D. Beintema, Vista, and Donald F. Dn'eschman,

Leucadia, Calif., assignors to Hughes Aircraft Company, Culver City, Calif a corporation of Delaware Filed Dec. 15, 1966, Ser. No. 602,015 Int. Cl. H01j 17/04, 17/30 US. 'Cl. 313218 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to high intensity flashlamps and more particularly to a novel and improved high intensity flashlamp which includes an ignition means which provides rapid, uniform ignition and institution of an are between electrodes.

High intensity flashlamps in the prior art are presently constructed of tungsten electrodes and ignition wires and also use high internal gas pressures therein. The reliability of these prior art lamps is sometimes questionable because arc blowout occurs between electrodes even though high accuracy is maintained in the lamp construction. This is due to contaminations in the base materials which cause erratic ignition, burning and reducing lifetime. Also, another problem in these prior art methods is that the arc has a tendency to wander between the electrodes from their original contact points.

It has been found that the electrodes may be the principal reason for the erratic behavior of the arc during operation of the lamps. In practice, a groove is cut in each electrode to accept the ignition wire and allow it to be placed in the central position on the electrodes. Upon applying a potential across the electrodes, the ignition wire is depleted rapidly upon ignition, thus establishing the are between the electrodes. This arc has a tendency to wander and blow out between the points of the electrodes due to contaminations in the tungsten either permitting or preventing enhanced emission from the electrodes. The heat generating in the electrode may rapidly erode the points thereof and thus cause them to blunt or be rounded, thereby further causing the arc stability problems. The heat thus generated is transmitted back along electrodes causing strains at the quartz-totungsten-molybdenum seal which, together with the high internal pressure, can cause the lamp to fail.

One object of this invention is to provide a novel and improved high intensity flashlamp which includes a uniform, rapid depletion of the ignition wire to establish anlarc between the electrodes.

Another object of this invention is to provide a novel and improved high intensity flashlamp which has an are between electrodes which does not wander or blow out.

Another object of this invention is to provide a novel and improved high intensity flashlamp which includes electrodes which do not blunt or erode and which thereby increase are stability.

These and other objects, features and advantages of the invention will become more apparent in the course of the following description and from an examination of the related drawings, wherein:

FIG. 1 is a central vertical sectional view through a preferred embodiment of the invention, and

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.

Turning now to a more detailed description of this invention, an envelope 10 which may be composed of aluminosilicate glass is provided to contain a pair of electrodes 12 and 14 and an ignition wire 16. In the preferred embodiment of this invention the' aluminosilicate glass tube 10 is provided with a outside diameter and has a precision bore therein. Electrodes 12 and 14 within the flashlamp glass envelope 10 may be composed of pyrolytic graphite. Such a material is used because it will electrically conduct in a direction which is longitudinal to its elongated axis and thermally conduct in an axis normal to this elongated axis. It should be understood that the pyrolytic graphite used in this invention is only a preferred embodiment and that other materials which exhibit these properties can be substituted therefor.

It may be that only the tips of electrodes 12 and 14 could be made of the pyrolytic graphite or that tungsten electrodes could be overlaid with a coating of pyrolytic graphite grown with C axis at to electrodes 12 and 14. The proper orientation of this material would allow the heat to be confined to the active tip and thereby stabilizing the arc and minimizing the heat transfer back along electrodes 12 and 14.

As is shown in the drawing, electrodes 12 and 14 may be conical shaped to fit within the bore of envelope 10. Ignition wire 16 is then fitted between the points of electrodes 12 and 14 in a conventional and suitable manner. This may be done by inserting the ignition wire in grooves cut in electrodes 12 and 14.

Envelope 10 is then sealed off by the glass-to-metal seals 18 and 20 at either end thereof in a suitable manner.

A stainless steel or copper terminal 22 is in electrical contact with electrode 12. Terminal 22 may be in the form of a tube for subjecting envelope 10 to a rare gas atmosphere or to fill it with high internal gas pressures. Terminal 22 can then be pinched off to seal envelope 10 and provide one electrical contact point thereof.

Having thus explained one embodiment of this invention, what is claimed is:

1. A high intensity lamp comprising:

a glass envelope, said glass envelope being hermetically sealed and subjected to an inert gas atmosphere;

a first and second electrode formed by pyrolytic graphite, said first and second electrodes being spaced apart and positioned within said glass envelope, said first and said second electrodes being composed of a material which is thermally conductive in a direction normal to the direction of electrical conduction; and

an ignition wire, said ignition wire being coupled between said first and said second electrodes.

2. A high intensity lamp according to claim 1, wherein said electrodes are electrically conductive along their longitudinal axis and are thermally conductive in a direction generally radial to the longitudinal axis.

3. A high intensity lamp comprising a hermetically sealed transparent envelope, first and second electrodes disposed within said envelope and in spaced relation to each other, each of said electrodes being formed to provide a tip area, the tip area of the respective electrodes being in adjacent relationship to each other, an ignition wire physically interconnecting the electrodes in the tip tive in a direction paralleling their longitudinal axes, said electrodes being thermally conductive in a direction generally radial to their longitudinal axes.

References Cited UNITED STATES PATENTS 4 2,013,371 9/1935 Van Liempt et al. 431-94 3,262,070 7/1966 Reuter et al. 331-94.S 3,262,071 7/1966 Reuter et al. 43192 X JAMES W. LAWRENCE, Primary Examiner R. F. HOSSFELD, Assistant Examiner US. Cl. X.R. 

